This application claims the benefit of Singapore Patent Application number 9906210-1, which was filed Dec. 9, 1999.
The present invention refers to a powder composition and to a method for polishing stone, in particular granite, said method making use of said powder composition.
Compounds and methods for polishing stone are known in the state of art. For example, U.S. Pat. No. 4,898,598 discloses a method for a polishing stone wherein the compound is a mixture of metallic oxides, a resin and a prepared gel, which compound is utilized in conjunction with sandpaper of varying grits to provide a smooth high gloss finish to the cut, rough-edged stone or marble.
U.S. Pat. No. 5,104,421 refers to a polishing method and abrasive pads, wherein the pad is manufactured with an abrasive such as alumina, zirconium oxide, tin oxide and cerium oxide, a kind of water-soluble cellulose ether and a kind of a solubilising agent. The substances above are blended and coated on a sheet-like substrate and, in the polishing process, only water is put between the rotating abrasive pads and the goods to be polished.
U.S. Pat. No. 5,462,568 discloses a universal stone polishing composition which includes an abrasive constituent and a composition which is a source of group Ia or group IIa metal ions when mixed with water.
A further composition and a method for polishing stone are disclosed in U.S. Pat. No. 5,551,960. According to said US patent, use is made of an abrasive article suitable for refining stone comprising an abrasive composite bonded to a backing, wherein the abrasive particles are dispersed in a binder.
Similarly, U.S. Pat. No. 5,942,015 discloses abrasive slurries, abrasive and articles made from the abrasive slurries. Furthermore, methods for the production of the abrasive articles are disclosed. The abrasive slurries and abrasive articles made therefrom comprise at least two grades of abrasive particles, i.e., a first larger grade and a second smaller grade wherein the abrasive grades have a medium particle size ratio of about 2 where the medium particle size ratio equals of the medium particle size of a larger grade of abrasive particles divided by the medium particle size of any smaller grade of abrasive particles.
The abrasive compositions according the state of art have the disadvantages that most of the abrasive particles have to be dispersed in a binder and to be coated onto a backing which is then placed on a pad of a scrubbing machine. This process is time and cost consuming as the pads have to be replaced from time to time.
Furthermore, the methods for polishing stone, in particular granite, have been carried out in the state of art in a process comprising several steps, approximately 5 to 7 and making use of polishing pads having different grits from 30 to 3500 microns. At the beginning, a polishing pad with grits of 3500 microns, in the next step a polishing pad having smaller grits, and so on, until in the last step, a polishing pad having grits having 30 to 100 microns are used to obtain a glossy surface again. As it can be taken from the afore, a lot of process steps are necessary in order to obtain satisfying results for the polished surface. Therefore, it is a long existing need for an improved process and an improved composition for polishing stone, in particular granite, which allows a more rapid polishing process. The inventors of the present invention surprisingly found that a powder composition of stannic oxide and a nickel-iron alloy can be used for obtaining superior results when being used in the inventive polishing method merely comprising two process steps.